The OptiTrack Active Tracking solution allows synchronized tracking of active LED markers using an OptiTrack camera system. The active tracking solution mainly consists of the Base Station and the active markers. The active markers can either be active markers on the Tag and/or markers on the active puck which can act as a single rigid body.

The Base Station connects to the camera system and sends out RF signals to the Tags, or pucks, allowing precise synchronization between camera exposure and illumination of the LEDs. Together, they allow Motive to recognize individual active markers in the software, and with labeled markers, more stable rigid body tracking can be achieved. The active markers will never be mislabeled and unique marker placements are no longer be required for distinguishing multiple rigid bodies.

A self-contained trackable object which can provide 6 DoF tracking information for any abritary objecct that it's attached to. Carries a factory installed Active Tag with 8 LEDs and a rechargeable battery with up to 10 hour run time on a single charge. The active pucks can also be attached to hands and feet of a player for rigid body skeleton tracking.

For best performance, place the base station near the center of your tracking space, with unobstructed lines of sight to the areas where your Active Tags will be located during use. Although the wireless signal is capable of traveling through many types of obstructions, there still exists the possibility of reduced range as a result of interference, particularly from metal and other dense materials.

Do not place external electromagnetic or radio frequency devices near the Base Station.

When Base Station is working properly, the LED closest to the antenna should blink in green when Motive is running. For more information: Base Station LED Indicators.

Press the power button for 1~2 seconds and release. The top-left LED will illuminate in orange while it initializes. Once it initializes the bottom LED will light up green if it has made a successful connection with the base station. Then the top-left LED will start blinking in green indicating that the sync packets are being received.

(Default: Passive) The Marker Labeling Mode setting determines whether the point cloud engine reconstructs passive markers, active markers, or both passive and active markers. When Motive is configured to one of the active marker tracking modes, it will be indicated on the perspective view pane.

Calibration Wanding:

When performing calibration wanding, please configure this to the default Passive Markers Only setting. There are known problems with wanding in one of the active marker labeling modes. This applies for both passive marker calibration wands and IR LED wands.

(Default: True) This should be set to true for stable active marker tracking. When enabled, the point cloud engine uses only the active marker centroids that have the matching active IDs to create a reconstruction. Even if the tracking rays intersect within the allowable residual offset, any centroids with mismatching IDs will be rejected and will not contribute to the reconstruction.

(Default: 12) This setting sets the complexity of the active illumination patterns. When tracking a high number of rigid body, this may need to be increased to allow for more combinations of the illumination patterns on each marker. When this value is set too low, duplicate active IDs will be produced. In most applications, the default value can be used.

For tracking the active markers, set the camera exposures a bit higher compared to when tracking passive markers. This allows the cameras to better detect the active markers. The optimal value will vary depending on the camera system setups, but in general, you would want to set the camera exposure between 400 ~ 750, microseconds.

Once the above settings have been configured, active markers will be reconstructed and tracked in Motive. From the unique illumination patterns, each active marker gets labeled individually, and a unique marker ID gets assigned to the corresponding reconstruction in Motive. These IDs can be monitored in the Live-reconstruction mode or in the 2D Mode. To check the marker IDs of respective reconstructions, enable the Marker Labels option under the visual aids (), and the IDs of selected markers will be displayed in the 3D viewport. The marker IDs assigned to active marker reconstructions are unique, and it can be used to point to a specific marker within many reconstructions in the scene.

Rigid body definitions that are created from actively labeled reconstructions will search for specific marker IDs along with the marker placements to track the rigid body. Further explained in the following section.

Duplicate active frame IDs

For the active label to properly work, it is important that each marker has a unique active IDs. When there are more than one markers sharing the same ID, there may be problems when reconstructing those active markers. In this case, the following notification message will show up. If you see this notification, please contact support to change the active IDs on the active markers.

In recorded 3D data, the labels of the unlabeled active markers will still indicate that it is an active marker. As shown in the image below, there will be Active prefix assigned in addition to the active ID to indicate that it is an active marker. This applies only to individual active markers that are not auto-labeled. Markers that are auto-labeled using a trackable model will be assigned with a respective label.

When a trackable asset (e.g. rigid body) is defined using active markers, it's active ID information gets stored in the asset along with marker positions. When auto-labeling the markers in the space, the trackable asset will additionally search for reconstructions with matching active ID, in addition to the marker arrangements, to auto-label a set of markers. This can add additional guard to the auto-labeler and prevents and mis-labeling errors.

Rigid body definitions created from actively labeled reconstructions will search for respective marker IDs in order to solve the rigid body. This gives a huge benefit because the active markers can be placed in perfectly symmetrical marker arrangements among multiple rigid bodies and not run into labeling swaps. With active markers, only the 3D reconstructions with active IDs stored under the corresponding rigid body definition will contribute to the solve.

If a rigid body was created from actively labeled reconstructions, the corresponding Active ID gets saved under the corresponding rigid body properties. In order for the rigid body to be tracked, the reconstructions with matching marker IDs in addition to matching marker placements must be tracked in the volume. If the active ID is set to 0, it means no particular marker ID is given to the rigid body definition and any reconstructions can contribute to the solve.

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